1. Field of the Invention
The present invention relates to wireless communication and, more particularly, to a method of transmitting and receiving multicast broadcast service.
2. Related Art
Multicast/Broadcast Service (hereinafter referred to as ‘MBS’) is a point-to-multipoint communication system in which one source transmits data packets to a plurality of destinations at the same time. Broadcast service refers to service in which data packets are transmitted to all users, and multicast service refers to service in which data packets are transmitted to a specific group. MBS is used in IEEE 802.16e which is one of mobile communication standards and referred to as MultiCast BroadCast Service (MCBCS) in WiMAX. The MBS is referred to as Evolved-MBS (E-MBS) in an IEEE 802.16m standard evolved from the IEEE 802.16e standard. Meanwhile, in the WCDMA standard of the 3rd Generation Partnership Project (3GPP), a standard called Multimedia Broadcast Multicast Service (MBMS) was established in Rel. 5 and is called Evolved MBMS (E-MBMS) after Rel. 8 which is referred to as Long Term Evolution (LTE). The terms named in the respective standards are slightly different, but standardization activities for them are being actively performed for the purpose of providing broadcasting communication convergence service.
FIG. 1 illustrates a frame structure for transmitting MBS data.
Referring to FIG. 1, a radio frame is composed in the unit of a superframe. One superframe consists of four frames. Each of the frames consists of a plurality of subframes. The first subframe of each superframe includes a Superframe Header (SFH). The SFH refers to the unit in which several frames are transmitted and chiefly includes the essential system parameter or system configuration information. The SFH includes a Primary Superframe Header (P-SFH) and can periodically include a Secondary Superframe Header (S-SFH). The P-SFH is chiefly transmitted every superframe. The P-SFH defines whether an S-SFH has been transmitted and changed, and the P-SFH is transmitted in a cycle of one or more superframes.
MBS has specific Quality of Service (QoS) and one service flow. The MBS is mapped to several terminals and supplied thereto at the same time. A terminal which receives MBS configures a corresponding parameter and service flow in order to receive corresponding service. A base station which provides MBS belongs to at least one MBS zone, and it is distinguished by an MBS zone ID. In each MBS zone, common contents are distinguished by a multicast STID (hereinafter referred to as E-MBS ID) and transmitted using a service flow. The E-MBS ID is a common ID which is assigned to a terminal in order to receive MBS. The MBS contents have the same channel (or service Flow ID (FID)). The FID is paired with a corresponding E-MBS ID for every MBS connection.
A single terminal can be assigned several FIDs. MBS contents belonging to one E-MBS ID are distinguished by FIDs and transmitted. In an MBS zone, a user must be able to receive MBS irrespective of whether the user is in a connected state or an idle state. It means that additional registration or procedure is not required in order to receive MBS. Further, when a terminal moves from one MBS zone to the other MBS zone, the terminal must be able to consistently receive MBS irrespective of a mode of the terminal.
When taking an MBS-unique frame structure and various parameters into consideration, there is a need for a frame structure and a control channel structure for efficiently transmitting MBS and detailed technology regarding an MAP message.